There are many applications for detecting infrared (IR) radiation. IR can refer to radiation having wavelengths longer than visible light (>0.7 μm) up to about 14 μm, with near-IR being a subset referring to wavelengths from about 0.7 μm to about 1.0 μm. One application is the detection of IR in environments with low ambient light, which can occur, for example, at night. It can also be useful to display to a user the image of the detected IR at a wavelength visible to the user. One common device for detecting IR images and displaying the detected images to a user is night-vision goggles.
Conventional night vision goggles are complex electro-optical devices that can require very high operating voltages and cost thousands of dollars. Typical night vision goggles intensify existing light instead of relying on their own light source and are sensitive to a broad spectrum of light, from visible through infrared. A conventional lens, called the objective lens, captures ambient light, including some near-infrared light. The gathered light is then sent to an image-intensifier tube. The tube outputs a high voltage, e.g., about 5,000 volts, to the image-tube components. The image-intensifier tube has a photo cathode, which is used to convert the photons of light energy into electrons. As the electrons pass through the tube, similar electrons are released from atoms in the tube, multiplying the original number of electrons by a factor of thousands through the use of a micro channel plate (MCP) in the tube. When the electrons from the photo cathode hit the first electrode of the MCP, they are accelerated into the glass micro channels by the 5,000-V bursts being sent between the electrode pair. As electrons pass through the micro channels, they cause thousands of other electrons to be released in each channel using a process called cascaded secondary emission. These new electrons also collide with other atoms, creating a chain reaction that results in thousands of electrons leaving the channel where only a few entered. At the end of the image-intensifier tube, the electrons hit a screen coated with phosphors. These electrons maintain their position in relation to the channel they passed through, which provides a perfect image since the electrons stay in the same alignment as the original photons. The energy of the electrons causes the phosphors to reach an excited state and release photons. These phosphors create the green image on the screen that has come to characterize night vision. The green phosphor image is viewed through another lens called the ocular lens, which allows you to magnify and focus the image. The night vision device may be connected to an electronic display, such as a monitor, or the image may be viewed directly through the ocular lens.
Accordingly, there is a need for IR sensors/detectors, and IR sensor/detector-display combinations, that operate at low operating voltages and are lightweight and cost-effective to produce.